It is known that the manufacture of blocks and of the relative veneers in multilaminar wood is performed by feeding in sequence a plurality of thin sheets of wood and stacking them, interposing between one sheet and another a layer of adhesive, until a single body having a desired thickness is formed. Subsequently, the aforementioned body made up of sheets alternating with layers of glue is compacted by a pressing action which causes the body to assume a thickness equal to the final thickness.
The adhesive usually employed for the manufacture of boards in multilaminar wood is a bonding mixture based on urea-formaldehyde resins. This type of additive has hitherto shown itself to be the only one capable of satisfying the requirements imposed by the production of multilaminar wood boards, and in particular:    chemical and physical stability in the storage phase;    reactivity and viscosity suitable for the technology used for application to wood veneers;    possibility of being coloured at the time of application;    ease of washing at the end of processing;    degree of elasticity such as to allow the multilaminar wood block to be subsequently sliced;    bonding power such as to allow good workability of the block thus obtained;    relatively low toxicity.
With reference to the toxicity, it is due principally to the formaldehyde included in the bonding mixture, which is considered capable of causing damage to human health. Current legislation therefore specifies ever smaller quantities of formaldehyde, and frequently this entails studies carried out by companies in the sector to reduce the quantities of this compound while however maintaining unaltered all the other properties of the adhesive.
In this connection, starting from glues based on urea-formaldehyde resin, the composition is altered by means of suitable additives (formaldehyde sequestrants, melamine resins, hardeners etc.) so as to have available a bonding mixture capable of satisfying the specified requirement of low toxicity. In the light of the above, the currently known bonding mixtures inevitably have an unavoidable minimum of formaldehyde, and this to a growing extent increases the problems relating to the use of these bonding mixtures for the manufacture of multilaminar wood blocks.
Other types of adhesives or bonding mixtures are currently known which are free from formaldehyde; however, they are not suitable for use in the manufacture of multilaminar wood blocks because they have unsuitable properties for satisfying the above requirements. In particular, one of the principal disadvantages is due to the excessive rapidity of setting of these bonding mixtures, which cure before the multilaminar wood block is completed, making it impossible to correctly carry out the compaction phase of the superimposed sheets.
It should in fact be noted that the production of a multilaminar wood block requires the coupling together of 300-1500 veneers which must be spread with adhesive, joined together and then pressed before the adhesive cures.
It is also necessary to ensure the satisfaction of all the other requirements of the finished product, referred to above, which depend heavily on the adhesive used, which will in fact be found interposed between the 300-1500 thin sheets (veneers) of wood.
In general, then, adhesives which are not urea-formaldehyde based are not able to ensure, once curing is complete, the correct elasticity to allow the multilaminar wood to be sliced.
In this situation, in certain instances, the technical task is to propose a multilaminar wood block, and a method for the manufacture thereof, capable of obviating the disadvantage mentioned above.
Within the scope of this technical task it is an object to make available a multilaminar wood block, and a method for the manufacture thereof, which achieve a very low level if not indeed a complete lack of toxicity.
In certain instances, it is a further object to make available a multilaminar wood block, and a method for the manufacture thereof, which use a bonding mixture capable of satisfying the requirements listed above, and in particular which have a curing time sufficient to allow the stacking of a predetermined number of sheets.
In certain instances, it is also an objective to make available a multilaminar wood block which can be correctly sliced without being ruined or ruining the cutting tools.
These objects, and yet others, are substantially achieved by a multilaminar wood block and a method for the manufacture thereof, having respectively the technical characteristics set forth in the independent claims and/or in one or more of the claims dependent upon them.
The description is now set forth, by way of example but without exclusive effect, of an embodiment of a multilaminar wood block, and a method for the manufacture thereof, in accordance with the attached drawings.